1663691 has 4 divisors (see below), whose sum is σ = 1675800. Its totient is φ = 1651584.

The previous prime is 1663687. The next prime is 1663693. The reversal of 1663691 is 1963661.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1663691 - 2² = 1663687 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1663693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5846 + ... + 6123.

It is an arithmetic number, because the mean of its divisors is an integer number (418950).

2^1663691 is an apocalyptic number.

1663691 is a deficient number, since it is larger than the sum of its proper divisors (12109).

1663691 is a wasteful number, since it uses less digits than its factorization.

1663691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12108.

The product of its digits is 5832, while the sum is 32.

The square root of 1663691 is about 1289.8414631264. The cubic root of 1663691 is about 118.4925072559.

The spelling of 1663691 in words is "one million, six hundred sixty-three thousand, six hundred ninety-one".